Active inductor and amplifier circuit

ABSTRACT

According to an embodiment, an active inductor has a first conductivity type MOS transistor with a source that is connected to an electrical power source supply line and a drain that is connected to an output terminal. It has a capacitance between a gate of the first conductivity type MOS transistor and the electrical power source supply line. It has a diode element that is connected between a drain and a gate of the first conductivity type transistor. It has an electric current source that supplies a bias electric current in a forward direction to the diode element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2016-256122, filed on Dec. 28, 2016; theentire contents of which are incorporated herein by reference.

FIELD

The present embodiment generally relates to an active inductor and anamplifier circuit.

BACKGROUND

A technique has conventionally been disclosed for an active inductorthat has a characteristic that corresponds to an inductor, by combininga passive element such as a resistor or a capacitor with an activeelement such as a transistor, and an amplifier circuit with such anactive inductor that is provided as a load thereof.

A direct electric current electric voltage drop at a load of anamplifier circuit causes reduction of a dynamic range of such anamplifier circuit. Furthermore, a frequency characteristic of anamplifier circuit is influenced by a frequency characteristic of a load.Hence, an active inductor with a small electric voltage drop and astable frequency characteristic is desired.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a configuration of an active inductoraccording to a first embodiment.

FIG. 2 is a diagram for illustrating a characteristic of an activeinductor according to a first embodiment.

FIG. 3 is a diagram illustrating a configuration of a differentialamplifier circuit according to a second embodiment.

FIG. 4 is a diagram illustrating a frequency characteristic of adifferential amplifier circuit according to a second embodiment.

FIG. 5 is a diagram illustrating a configuration of an active inductoraccording to a third embodiment.

FIG. 6 is a diagram illustrating a configuration of a differentialamplifier circuit according to a fourth embodiment.

DETAILED DESCRIPTION

According to an embodiment, an active inductor has a first conductivitytype MOS transistor with a source that is connected to an electricalpower source supply line and a drain that is connected to an outputterminal. It has a capacitance between a gate of the first conductivitytype MOS transistor and the electrical power source supply line. It hasa diode element that is connected between a drain and a gate of thefirst conductivity type transistor. It has an electric current sourcethat supplies a bias electric current in a forward direction to thediode element.

Hereinafter, an active inductor and an amplifier circuit according to anembodiment will be described in detail, with reference to theaccompanying drawings. Additionally, the present invention is notlimited by such an embodiment.

First Embodiment

FIG. 1 is a diagram illustrating a configuration of an active inductoraccording to a first embodiment. An active inductor 1 according to thepresent embodiment includes a PMOS transistor 11 with a source that isconnected to an electrical power source supply line 10 where anelectrical power source electric voltage VDD is applied thereto. A drainof the PMOS transistor 11 is connected to an output terminal 15.

It has an NMOS transistor 12 that composes diode connection, between agate and a drain of the PMOS transistor 11. The NMOS transistor 12 isprovided with a drain and a gate that are connected to a drain of thePMOS transistor 11 and a source that is connected to a gate of the PMOStransistor 11. In a case where the NMOS transistor 12 composes a diodeelement, an electric current flows from a drain to a source of such anNMOS transistor so as to provide a forward bias state.

It has a capacitor 13 between a gate of the PMOS transistor 11 and theelectrical power source supply line 10. The capacitor 13 may be composedof a capacitive element such as a capacitor or may be composed of aparasitic capacitance between a gate and a source of the PMOS transistor11.

An electric current source 14 is connected to a source of the NMOStransistor 12. The electric current source 14 supplies a bias electriccurrent in a forward direction to the NMOS transistor 12.

A small-signal impedance Z_(AY) between the electric current sourcesupply line 10 and the output terminal 15 according to the presentembodiment is represented by a following formula (1).

$\begin{matrix}{Z_{A\; 1} = \frac{1 + \frac{s \cdot C}{g_{mN}}}{g_{mP} + {s \cdot C}}} & (1)\end{matrix}$

In formula (1), g_(mp) demotes a transfer conductance of the PMOStransistor 11, g_(mN) denotes a transfer conductance of the NMOStransistor 12, s denotes a Laplace transformation factor, and C denotesa capacitance value of the capacitor 13. From formula (1), it ispossible to find that it has a characteristic of an active inductor.

An electric voltage drop V_(PX) between a source and a drain of the NMOStransistor 12, that is, between a point P and a point X as illustratedin FIG. 1, is represented by a following formula (2). Additionally, thePMOS transistor 11 and the NMOS transistor 12 are operated in asaturation region.

$\begin{matrix}{V_{PX} = {V_{thN} + \sqrt{\frac{2 \cdot I_{A}}{\mu_{N} \cdot C_{OX} \cdot {W_{N}/L_{N}}}}}} & (2)\end{matrix}$

In formula (2), V_(thN) denotes a threshold value of the NMOS transistor12, μ_(N) denotes a mobility of an electron, C_(OX) denotes a thicknessof a gate oxide film of the NMOS transistor 12, W_(N) denotes a gatewidth, L_(N) denotes a gate length, and I_(A) denotes an electriccurrent value of the electric current source 14. It is possible toignore a gate electric current of the PMOS transistor 11, and hence, anelectric current I_(A) that is supplied from the electric current source14 is substantially a bias electric current of the NMOS transistor 12.

FIG. 2 is a diagram for illustrating a characteristic of an activeinductor according to the first embodiment. A horizontal axis indicatesan electric current value I_(A) of the electric current source 14 and avertical axis indicates a simulation result of an electric voltage dropV_(PX) between the point P and the point X. In FIG. 2, a characteristiccurve 100 indicates a simulation result of the active inductor 1. Acharacteristic curve 200 indicates a simulation result in a case where aresistor is connected instead of the NMOS transistor 12.

As indicated by the characteristic curve 100, it is possible for theactive inductor 1 to obtain a large electric voltage drop even in a casewhere a bias electric current is small. An electric voltage drop V_(PX)is an electric voltage that raises an electric potential at the point Pwith respect to an electric potential at the point X toward anelectrical power source electric voltage VDD side. That is, an electricpotential at the point P is higher than an electric potential at thepoint X by an electric voltage drop V_(PX) caused by NMOS transistor 12.It is possible for the NMOS transistor 12 to generate a large electricvoltage drop V_(PX) as a small electric current, and hence, it ispossible to suppress reduction of an electric voltage at the outputterminal 15 efficiently. Thereby, in a case where the active inductor 1is used as a load, it is possible to suppress a direct electric currentelectric voltage drop at such an load, and hence, it is possible toreduce an electrical power source electric voltage VDD so that it ispossible to attain reduction of an electric voltage or reduction of anelectrical power consumption.

An impedance Z_(AI) of the active inductor 1 is represented by acapacitance C, a transfer conductance g_(mP) of the PMOS transistor 11,and a transfer conductance g_(mN) of the NMOS transistor 12 as indicatedby formula (1). It is possible to adjust transfer conductances g_(mP)and g_(mN) by bias electric currents that are supplied to the PMOStransistor 11 and the NMOS transistor 12, respectively. Accordingly, avariation factor of an impedance Z_(AI) is only a capacitance C, andhence, it is possible to provide a stable impedance. Thereby, in a casewhere the active inductor 1 is used as a load, circuit design isfacilitated.

Additionally, as indicated by the characteristic curve 200 in a casewhere a configuration is provided by using a resistor, a bias electriccurrent that flows through such a resistor is increased to raise anelectric potential at the output terminal 15, so that it is possible toreduce an electric voltage drop caused by the active inductor 1.However, in such a case, an increase of a bias electric current causesan increase of electrical power consumption.

Second Embodiment

FIG. 3 is a diagram illustrating a configuration of a differentialamplifier circuit according to a second embodiment. A component thatcorresponds to that of the first embodiment will be provided with anidentical symbol, and a redundant description thereof will be providedonly in a case where it is needed. A similar matter applies to a latterpart. A differential amplifier circuit according to the presentembodiment has NMOS transistors 41, 42 with sources that are commonlyconnected to compose a differential pair between electrical power sourcesupply lines 10, 20. A ground electric potential VSS is applied to theelectrical power source supply line 20. An active inductor 1A as a loadis connected to a drain of the NMOS transistor 41 and an active inductor1B as a load is connected to a drain of the NMOS transistor 42.

The active inductors 1A, 1B have a configuration identical to that ofthe active inductor 1 as illustrated in FIG. 1. An NMOS transistor 24 ofthe active inductor 1A is connected between a capacitor 13 and theelectrical power source supply line 20 and composes an electric currentsource that supplies a bias electric current I_(A) in a forwarddirection to an NMOS transistor 12.

The active inductor 1B includes a PMOS transistor 21 with a source thatis connected to the electrical power source supply line 10. A drain ofthe PMOS transistor 21 is connected to a signal output terminal 46. Ithas an NMOS transistor 22 that composes diode connection, between a gateand a drain of the PMOS transistor 21. The NMOS transistor 22 isprovided with a drain and a gate that are connected to a drain of thePMOS transistor 21 and a source that is connected to a gate of the PMOStransistor 21.

It has a capacitor 23 between a gate of the PMOS transistor 21 and theelectrical power source supply line 10. The capacitor 23 may be composedof a capacitive element such as a capacitor or may be composed of aparasitic capacitance between a gate and a source of the PMOS transistor21.

A source of the NMOS transistor 22 is connected to a drain of an NMOStransistor 25. The NMOS transistor 25 is connected between the capacitor23 and the electrical power source supply line 20 and composes anelectric current source that supplies a bias electric current in aforward direction to the NMOS transistor 22. Due to the NMOS transistor22, an electric voltage drop V_(YQ) that is generated between a point Yand a point Q as illustrated in FIG. 3 acts to raise an electricpotential at a drain of the PMOS transistor 21 toward an electricalpower source electric voltage VDD side, and suppresses a direct electriccurrent electric voltage drop caused by the active inductor 1B.

An NMOS transistor 40 is connected between a common source of the NMOStransistors 41, 42 and the electrical power source supply line 20 andsupplies bias electric currents to the NMOS transistors, 41, 42. TheNMOS transistors 24, 25, 40 are biased by a common bias circuit 30.Gates of the NMOS transistors 41, 42 are connected to signal inputterminals 43, 44, respectively. Capacitors 50, 51 represent capacitiveloads where output signals from signal output terminals 45, 46 aresupplied thereto.

The bias circuit 30 has NMOS transistors 33 and 34 with commonlyconnected gates. Gates of the NMOS transistors 33, and gates of the NMOStransistors 24, 25, 40 are commonly connected to compose a currentmirror circuit.

A resistor 35 is connected between a source of the NMOS transistor 33and the electrical power source supply line 20. A drain of the NMOStransistor 33 is connected to a drain and a gate of a PMOS transistor31. A source of the PMOS transistor 31 is connected to the electricalpower source supply line 10. A drain of the NMOS transistor 34 isconnected to a drain of a PMOS transistor 32. The transistor 32 isprovided with a source that is connected to the electrical power sourcesupply line 10 and a gate that is connected to a gate of the PMOStransistor 31.

The bias circuit 30 is of an electric voltage insensitive type that isnot influenced by a variation of an electrical power source electricvoltage VDD, and a drain electric current I of the NMOS transistor 33 isrepresented by formula (3).

$\begin{matrix}{I = {\frac{2}{\mu_{N} \cdot C_{OX}} \cdot \frac{L_{N}}{W_{N}} \cdot \frac{1}{R_{s}^{2}} \cdot \left( {1 - \frac{1}{\sqrt{K}}} \right)^{2}}} & (3)\end{matrix}$

In formula (3), μ^(N) denotes a mobility of an electron, C_(OX) denotesa thickness of a gate oxide film of the NMOS transistor 33, W_(N)denotes a gate width, L_(N) denotes a gate length, R_(s) denotes aresistance value of the resistor 35, and K denotes a ratio of a surfacearea of the NMOS transistor 33 to that of the NMOS transistor 34.

On the other hand, a transfer conductance g_(m) in a case where a biaselectric current that is an electric current I flows through a MOStransistor is represented by formula (4).

$\begin{matrix}{g_{m} = \sqrt{2 \cdot \mu \cdot C_{OX} \cdot \frac{W}{L} \cdot I}} & (4)\end{matrix}$

In formula (4), C_(OX) denotes a thickness of a gate oxide film, Wdenotes a gate width, and L denotes a gate length. μ is a mobility of acarrier that is a mobility of an electron in a case of an NMOStransistor or a hole in a case of a PMOS transistor.

Formula (3) is substituted for formula (4), and thereby, a relation asrepresented by formula (5) is obtained.

$\begin{matrix}{g_{m}\alpha{\frac{2}{R_{s}} \cdot \left( {1 - \frac{1}{\sqrt{K}}} \right)}} & (5)\end{matrix}$

The PMOS transistors 31 and 32 compose a current mirror circuit, andhence, in a case where such a surface area ratio is 1, an electriccurrent that is equal to an electric current I flows through the PMOStransistor 32. Accordingly, a surface area ratio of the NMOS transistors34, 24, 25, 40 is a predetermined ratio, and thereby, it is possible tosupply electric currents with a predetermined ratio relative to anelectric current I from the NMOS transistors 24, 25, 40 to the NMOStransistors 41, 42 and the NMOS transistors 12, 22.

An electric current I as represented by formula (3) is proportional toan inverse (1/μ_(N)) of a mobility μ_(N) of a carrier (electron). Atransfer conductance g_(m) as represented by formula (4) is proportionalto a mobility μ (a mobility μ_(N) of an electron in a case of an NMOStransistor), and hence, a term of a mobility μ of a carrier (electron)in a transfer conductance g_(m) of an NMOS transistor is canceled by anelectric current I to be supplied. That is, contribution of a mobility μto a transfer conductance g_(m) is canceled by supply of an electriccurrent I.

Accordingly, it is possible to cause transfer conductances g_(m) of theNMOS transistors 12, 22, 41, 42 to be stable values that are notinfluenced by a variation of an electric voltage. Moreover, a resistorwith a small temperature coefficient is used as the resistor 35, andthereby, it is possible to obtain a transfer conductance g_(m) with aless temperature change thereof.

FIG. 4 is a diagram illustrating a frequency characteristic of adifferential amplifier circuit according to the second embodiment. Acharacter curve 300 indicates a case where an electrical power sourceelectric voltage VDD is 0.95 V and a temperature is 125° C., and acharacteristic curve 400 indicates a case where an electrical powersource electric voltage VDD is 1.05 V and a temperature is −25° C.Electric currents that cancel contribution of a mobility μ of a carrierto a transfer conductance g_(m) are supplied to the NMOS transistors 12,22, 41, 42, and thereby, transfer conductances g_(m) of such NMOStransistors are stabilized. Thereby, it is possible to find that afrequency characteristic is indicated that is stable in a broadfrequency band with respect to an electrical power source electricvoltage VDD and a temperature change.

Furthermore, a small signal impedance Z_(AI) of the active inductor 1 isrepresented by formula (1). Therefore, a zero-point frequency f₀ of theactive inductor 1 is g_(mN)/2πC and a pole frequency f_(p) isg_(mP)/2πC. That is, it is possible to adjust any of the frequencies bytransfer conductances g_(mP), g_(mN), and hence, it is possible toexecute adjustment thereof by adjustment of bias electric currents thatare supplied to the PMOS transistor 11 and the NMOS transistor 12.Accordingly, adjustment of a frequency characteristic of a differentialamplifier circuit with an active inductor according to the presentembodiment that is provided as a load thereof is facilitated.

Furthermore, electric voltage drops in the active inductors 1A, 1B aresuppressed, and hence, it is possible to attain reduction of anelectrical power source electric voltage VDD so that it is possible toreduce electrical power consumption.

Third Embodiment

FIG. 5 is a diagram illustrating a configuration of an active inductoraccording to a third embodiment. An active inductor 1 according to thepresent embodiment has a configuration provided by replacing aconductivity type of a MOS transistor as illustrated in FIG. 1 that is aP type with an N type.

That is, the active inductor 1 includes an NMOS transistor 51 with asource that is connected to an electrical power source supply line 20. Adrain of the NMOS transistor 51 is connected to an output terminal 55.

It has a PMOS transistor 52 that composes diode connection, between agate and a drain of the NMOS transistor 51. The PMOS transistor 52 isprovided with a drain and a gate that are connected to a drain of theNMOS transistor 51 and a source that is connected to a gate of the NMOStransistor 51. In a case where the PMOS transistor 52 composes a diodeelement, a state where an electric current flows from a source to adrain thereof is a forward bias state.

It has a capacitor 53 between a gate of the NMOS transistor 51 and theelectrical powers source supply line 20. The capacitor 53 may becomposed of a capacitive element such as a capacitor or may be composedof a parasitic capacitance between a gate and a source of the NMOStransistor 51.

A source of the PMOS transistor 52 is connected to an electric currentsource 54. The electric current source 54 supplies a bias electriccurrent I_(B) in a forward direction to the PMOS transistor 52.

In the active inductor 1, an electric potential at a gate of the NMOStransistor 51 is higher than an electric potential at a drain thereof,due to an electric voltage drop V_(XP) of the PMOS transistor 52. Inother words, an electric voltage drop V_(XP) has a function of loweringan electric potential at a drain of the NMOS transistor 51 toward aground, electric potential VSS side relative to an electric potential ata gate thereof. Thereby, it is possible to suppress a rise of anelectric voltage at the output terminal 55. That is, it is possible tosuppress a direct electric current electric voltage drop caused by theactive inductor 1.

Similarly to the first embodiment, it is possible for the PMOStransistor 52 to generate a large electric voltage drop V_(XP) due to asmall bias electric current, and hence, it is possible to suppress adirect electric current electric voltage drop caused by the activeinductor 1 efficiently.

Fourth Embodiment

FIG. 6 is a diagram illustrating a configuration of a differentialamplifier circuit according to a fourth embodiment. In a differentialamplifier circuit according to the present embodiment, the activeinductor 1 of FIG. 5 is provided as a load.

A differential amplifier circuit according to the present embodiment hasPMOS transistors 81, 82 with sources that are commonly connected tocompose a differential pair. Gates of PMOS transistors 81, 82 areconnected to signal input terminals 83, 84. A drain of the PMOStransistor 81 is connected to an active inductor 1A as a load and adrain of the PMOS transistor 82 is connected to an active inductor 1B asa load.

The electric current source 54 that supplies an electric current I_(B)is composed of a PMOS transistor 55. A drain of an NMOS transistor 51 isconnected to a signal output terminal 85. The active inductor 1B has anNMOS transistor 61, PMOS transistors 62, 65, and a capacitor 63. Asource of the NMOS transistor 61 is connected to an electrical powersource supply line 20. A drain of the NMOS transistor 61 is connected toa signal output terminal 86.

It has the PMOS transistor 62 that composes diode connection, between agate and a drain of the NMOS transistor 61. The PMOS transistor 62 isprovided with a drain and a gate that are connected to a drain of theNMOS transistor 61 and a source that is connected to a gate of the NMOStransistor 61.

The capacitor 63 is connected between a gate of the NMOS transistor 61and the electrical power source supply line 20. The capacitor 63 may becomposed of a capacitive element such as a capacitor or may be composedof a parasitic capacitance between a gate and a source of the NMOStransistor 61.

A source of the PMOS transistor 62 is connected to a drain of the PMOStransistor 65. The PMOS transistor 65 composes an electric currentsource that supplies a bias electric current in a forward direction tothe PMOS transistor 62.

PMOS transistors 80, 55, 65 are biased by a common bias circuit 30.

That is, the bias circuit 30 has PMOS transistors 73 and 74 withcommonly connected gates. A resistor 75 is connected between a source ofthe PMOS transistor 73 and an electrical power source supply line 10.

A drain of the PMOS transistor 73 is connected to a drain and a gate ofan NMOS transistor 71. A source of the NMOS transistor 71 is connectedto the electrical power source supply line 20. A drain of the PMOStransistor 74 is connected, to a drain of ah NMOS transistor 72. TheNMOS transistor 72 is provided with a source that is connected to theelectrical power source supply line 20 and a gate that is connected to agate of the NMOS transistor 71.

A differential amplifier circuit according to the present embodiment hasthe PMOS transistors 81, 82 with the active inductors 1A, 1B that axeprovided as loads. Electric potentials at drains of the NMOS transistors51, 61 are lowered toward a ground electric potential VSS side byelectric voltage drops of PMOS transistors 52, 62, and thereby, electricvoltage drops at the active inductors 1A, 1B are suppressed.Accordingly, it is possible to lower direct electric current electricpotentials at the signal output terminals 85, 86 to broaden a dynamicrange, and hence, it is possible to attain reduction of an electricalpower source electric voltage VDD. Thereby, it is possible to suppresselectrical power consumption of a differential amplifier circuit.

In the present embodiment, it is possible to represent an electriccurrent I that flows through the PMOS transistor 73 by formula (3) wherea mobility μ_(N) is replaced with a mobility μ_(P) of a hole, C_(OX),W_(N), and L_(N) are replaced with a thickness of a gate oxide film, agate width, and a gate length of the PMOS transistor 73, respectively,R_(s) is a resistance value of the resistor 75, and K is a ratio of asurface area of the PMOS transistor 73 to that of the PMOS transistor74.

It is possible to represent transfer conductances g_(m) of the PMOStransistors 52, 62, 81, 82 by formula (4) where a mobility μ is replacedwith a mobility μ_(P) of a hole.

It is possible to supply electric currents that have a predeterminedratio relative to an electric current I that flows through the PMOStransistor 73 to the PMOS transistors 52, 62, 81, 82, due to the PMOStransistors 74, 55, 65, 80, respectively, and hence, it is possible tocause transfer conductances g_(m) of such PMOS transistors 52, 62, 81,82 to be a stable value that is not dependent on an electrical powersource electric voltage VDD.

That is, electric currents that are supplied from the PMOS transistors55, 65, 80 that are biased by the bias circuit 30 supply electriccurrents that cancel contribution of a mobility μ of a carrier (hole) totransfer conductances g_(m) of the PMOS transistors 52, 62, 81, 82, andhence, it is possible to stabilize transfer conductances g_(m) of suchPMOS transistors 52, 62, 81, 82. Thereby, it is possible to stabilize acircuit operation of a differential amplifier circuit. It is possible toobtain a transfer conductance g_(m) with a less temperature changethereof by using a resistor with a small temperature coefficient as sheresistor 75, and hence, it is possible to stabilize a circuit operationof a differential amplifier circuit. Thereby, a differential amplifiercircuit that has a stabilized frequency characteristic is providedsimilarly to the second embodiment.

The number of diode-connected MOS transistors is not limited to one. Forexample, multiple diode-connected MOS transistors are connected inseries, and thereby, it is possible to adjust an electric potential atan output terminal of an active inductor. It is also possible to usediode connection that connects a base and an emitter of a bipolartransistor, instead of a diode-connected MOS transistor.

Furthermore, a configuration with an active inductor that is provided asa load is not limited to a differential amplifier circuit. For example,it is also possible to compose an amplifier circuit in such a mannerthat the active inductor 1 according to an embodiment as a load isconnected to a drain of a MOS transistor with a gate that receives aninput signal and an output signal is output from an output terminal thatis connected to a drain of such a MOS transistor.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. An active inductor, comprising: a firstconductivity type first MOS transistor with a source, that is connectedto an electrical power source supply line and a drain that is connectedto an output terminal; a capacitance between a gate of the firstconductivity type first MOS transistor and the electrical power sourcesupply line; a diode element that is connected between the drain and thegate of the first conductivity type first MOS transistor; and anelectric current source that supplies a bias electric current in aforward direction to the diode element.
 2. The active inductor accordingto claim 1, wherein the diode element includes a second conductivitytype second MOS transistor with a drain and a gate that are connected tothe drain of the first conductivity type first MOS transistor and asource that is connected to the gate of the first conductivity typefirst MOS transistor.
 3. The active inductor according to claim 2,wherein the electric current source supplies an electric current thatcancels contribution of a mobility of a carrier to a transferconductance of the second conductivity type second MOS transistor. 4.The active inductor according to claim 2, wherein an electrical powersource electrical voltage is applied to the electrical power sourcesupply line, the first conductivity type first MOS transistor iscomposed of a PMOS transistor, and the second conductivity type secondMOS transistor is composed of an NMOS transistor.
 5. The active inductoraccording to claim 2, wherein a ground electrical voltage is applied tothe electrical power source supply line, the first conductivity typefirst MOS transistor is composed of an NMOS transistor, and the secondconductivity type second MOS transistor is composed of a PMOStransistor.
 6. The active inductor according to claim 4, wherein theelectric current source includes: a third NMOS transistor with a drainthat is connected to the gate of the first conductivity type first MOStransistor and a source that is supplied with a ground electric voltage;and a bias circuit that supplies a bias electric voltage to a gate ofthe third NMOS transistor, wherein the bias circuit includes: a fourthNMOS transistor with a gate that is connected to a gate of the thirdNMOS transistor and a source that is connected to a second electricalpower source supply line where the ground electric voltage is appliedthereto; a fifth NMOS transistor with a gate that is connected to thegate of the fourth NMOS transistor and a source that is connected to thesecond electrical power source supply line through a resistance element;a sixth PMOS transistor with s drain that is connected to the gate and adrain of the fourth NMOS transistor and a source that is connected tothe electrical power source supply line, and a seventh PMOS transistorwith a drain and a gate that are connected to a drain of the fifth NMOStransistor, a source that is connected to the electrical power sourcesupply line, and the gate that is connected to a gate of the sixth PMOStransistor.
 7. The active inductor according to claim 5, wherein theelectric current source includes: a third PMOS transistor with a drainthat is connected to the gate of the first conductivity type first MOStransistor and a source where an electrical power source electricvoltage is applied thereto; and a bias circuit that supplies a biaselectric voltage to a gate of the third PMOS transistor, wherein thebias circuit includes: a fourth PMOS transistor with a gate that isconnected to a gate of the third PMOS transistor and a source that isconnected to a second electrical power source supply line where theelectrical power source electric voltage is applied thereto; a fifthPMOS transistor with a gate that is connected to the gate of the fourthPMOS transistor and a source that is connected to the second electricalpower source supply line through a resistance element; a sixth NMOStransistor with a drain that is connected to the gate and a drain of thefourth PMOS transistor and a source that is connected to the electricalpower source supply line; and a seventh NMOS transistor with a drain anda gate that are connected to a drain of the fifth PMOS transistor, asource that is connected to the electrical power source supply line, andthe gate that is connected to a gate of the sixth NMOS transistor. 8.The active inductor according to claim 1, wherein the capacitance is aparasitic capacitance between the gate and the source of the firstconductivity type first MOS transistor.
 9. The active inductor accordingto claim 1, wherein the capacitance is composed of a capacitive element.10. An amplifier circuit with the active inductor according to claim 1that is provided as a load thereof.
 11. The amplifier circuit accordingto claim 10, comprising a second conductivity type second MOS transistorwith a gate that is supplied with an input signal, a drain that isconnected to the active inductor, and a source that is supplied with abias electric current.
 12. The amplifier circuit according to claim 10,wherein the amplifier circuit is a differential amplifier circuit thatincludes: a first load that has a configuration of the active inductor;a second load that has a configuration of the active inductor; a secondconductivity type second MOS transistor with a drain that is connectedto the first load and a gate that is connected to a first signal inputterminal; a second conductivity type third MOS transistor with a drainthat is connected to the second load and a gate that is connected to asecond signal input terminal; an electric current source that supplies abias electric current to a source of the second conductivity type secondMOS transistor and a source of the second conductivity type third MOStransistor; a first signal output terminal that is connected to thedrain of the second conductivity type second MOS transistor; and asecond signal output terminal that is connected to the drain of thesecond conductivity type third MOS transistor.
 13. The amplifier circuitaccording to claim 12, wherein the electric current source that suppliesthe bias electric current to the source of the second conductivity typesecond MOS transistor and the source of the second conductivity typethird MOS transistor includes: a second conductivity type fourth MOStransistor with a drain that is connected to the source of the secondconductivity type second MOS transistor and the source of the secondconductivity type third MOS transistor; and a bias circuit that suppliesa bias electric voltage to a gate of the second conductivity type fourthMOS transistor.
 14. An amplifier circuit, comprising: a first electricalpower source supply line where a first electric voltage is appliedthereto; a second electrical power source supply line where a secondelectric voltage is applied thereto; a bias circuit that is driven by anelectric voltage between the first electrical power source supply lineand the second electrical power source supply line and generates apredetermined bias electric voltage; a first conductivity type first MOStransistor, a first conductivity type second MOS transistor, and a firstconductivity type third MOS transistor, where biasing between gates andsources thereof is executed by the predetermined bias electric voltageof the bias circuit; a first conductivity type fourth MOS transistorwith a source that is connected to a drain of the first conductivitytype first MOS transistor, a gate that is connected to a second signalinput terminal, and a drain that is connected to a first signal outputterminal; a first conductivity type fifth MOS transistor with a sourcethat is connected to a drain of the first conductivity type first MOStransistor, a gate that is connected to a second signal input terminal,and a drain that is connected to a second signal output terminal; afirst active inductor that is connected between the drain of the firstconductivity type fourth MOS transistor and the first electrical powersource supply line; and a second active inductor that is connectedbetween the drain of the first conductivity type fifth MOS transistorand the first electrical power source supply line; wherein the firstactive inductor includes: a second conductivity type sixth MOStransistor with a source that is connected to the first electrical powersource supply line, a drain that is connected to the drain of the firstconductivity type fourth MOS transistor, and a gate that is con nee tedto a drain of the first conductivity type second MOS transistor; a firstcapacitance between the gate of the second conductivity type sixth MOStransistor and the first electrical power source supply line; and afirst diode element that is connected between the drain and the gate ofthe second conductivity type sixth MOS transistor, and wherein thesecond active inductor includes: a second conductivity type seventh MOStransistor with a source that is connected to the first electrical powersource supply line, a drain that is connected to the drain of the firstconductivity type fifth MOS transistor, and a gate that is connected toa drain of the first conductivity type third MOS transistor; a secondcapacitance between the gate of the second conductivity type seventh MOStransistor and the first electrical power source supply line; and asecond diode element that is connected between the drain and the gate ofthe second conductivity type seventh MOS transistor.
 15. The amplifiercircuit according to claim 14, wherein: the first capacitance of thefirst active inductor is composed of a parasitic capacitance between thegate and the source of the second conductivity type sixth MOStransistor, and the second capacitance of the second active inductor iscomposed of a parasitic capacitance between the gate and the source ofthe second conductivity type seventh MOS transistor.
 16. The amplifiercircuit according to claim 14, wherein: the first diode element of thefirst active inductor includes a first conductivity type eighth MOStransistor with a drain and a gate that are connected to the drain ofthe second conductivity type sixth MOS transistor and a source that isconnected to the gate of the second conductivity type sixth MOStransistor; and the second diode element of the second active inductorincludes a first conductivity type ninth MOS transistor with a drain anda gate that are connected to the drain of the second conductivity typeseventh MOS transistor and a source that is connected to the gate of thesecond conductivity type seventh MOS transistor.
 17. The amplifiercircuit according to claim 14, wherein: an electrical power sourceelectric voltage is applied to the first electrical power source supplyline; a ground electric voltage is applied to the second electricalpower source supply line; the first conductivity type first to fifth MOStransistors are composed of NMOS transistors; the second conductivitytype sixth and seventh MOS transistors are composed of PMOS transistors.18. The amplifier circuit according to claim 14, therein: a groundelectric voltage is applied to the first electrical power source supplyline; an electrical power source electric voltage is applied to thesecond electrical power source supply line; the first conductivity typefirst to fifth MOS transistors are composed of PMOS transistors; thesecond conductivity type sixth and seventh MOS transistors are composedof NMOS transistors.
 19. The amplifier circuit according to claim 17,wherein the bias circuit includes: a first conductivity type eighth MOStransistor with a gate that is connected to gates of the firstconductivity type first to third MOS transistors and a source that isconnected to the second electrical power source supply line; a firstconductivity type ninth MOS transistor with a gate that is connected tothe gate of the first conductivity type eighth MOS transistor and asource that is connected to the second electrical power source supplyline through a resistance element; a second conductivity type tenth MOStransistor with a drain that is connected to the gate and a drain of theeighth MOS transistor and a source that is connected to the firstelectrical power source supply line; and a second conductivity typeeleventh MOS transistor with a drain and a gate that are connected to adrain of the ninth MOS transistor, a source that is connected to thefirst electrical power source supply line, and the gate that isconnected to a gate of the second conductivity type tenth MOStransistor.
 20. The amplifier circuit according to claim 18, wherein thebias circuit includes: a first conductivity type eighth MOS transistorwith a gate that is connected to gates of the first conductivity typefirst to third MOS transistors and a source that is connected to thesecond electrical power source supply line; a first conductivity typeninth MOS transistor with a gate that is connected to the gate of thefirst conductivity type eighth MOS transistor and a source that isconnected to the second electrical power source supply line through aresistance element; a second conductivity type tenth MOS transistor witha drain that is connected to the gate and a drain of the eighth MOStransistor end a source that is connected to the first electrical powersource supply line; and a second conductivity type eleventh MOStransistor with a drain and a gate that are connected to a drain of thefirst conductivity type ninth MOS transistor, a source that is connectedto the first electrical power source supply line, and a gate that isconnected to a gate of the second conductivity type tenth MOStransistor.